1. Field of the Invention
The present invention is directed to powder actuated tools, and more particularly to a powder actuated fastener driving tool having automatic powder cartridge strip indexing.
2. Description of the Related Art
Powder actuated fastener setting tools are known generally. U.S. Pat. No. 5,429,291 entitled “Compression Actuated Tool For Driving Fasteners” assigned commonly with the present application, for example, discloses a powder driven tool including a manually operated spring biased indexing lever pivotally mounted thereon for advancing a magazine strip retaining a plurality of powder cartridges therein through a magazine channel of the tool.
For many powder actuated tools it is desirable to have a mechanism that indexes a strip of explosive powder cartridges after the tool has been fired so that a fresh cartridge is ready for firing without the operator having to do anything. An example of an indexing mechanism is disclosed in the commonly assigned patent application having the Ser. No. 09/689,095 entitled “Powder Driven Fastener Setting Tool,” the disclosure of which is incorporated herein by reference. The above referenced application teaches the use of a reciprocating sleeve which drives an indexing lever to index a strip of cartridges along a magazine channel. The sleeve reciprocates during firing of the tool, and is returned when an operator pushes the sleeve into its original position.
In some applications it may be desirable to make the indexing of the cartridge strip automatic, so that the operator does not have to perform the added step of pushing the reciprocating sleeve back into its original, pre-firing position. However, the indexing of the cartridge strip still must be driven by the motion of some part of the fastener driving tool. One possible part to use to drive the indexing of the cartridge strip is to use the motion of a trigger, wherein the trigger also actuates a firing mechanism of the tool. U.S. Pat. No. 6,272,782 to Dittrich et al. discloses a cartridge advancing mechanism linked to the trigger using connected pivoting levers.
A problem that has occurred with tools using pivoting levers has been “dead stop” of the trigger. When the trigger and advancing mechanism are directly linked, such as with connected pivoting levers, the trigger can come to a hard, or dead, stop when the advancing mechanism comes to a stop as it engages with the cartridge strip. Dead stopping can become uncomfortable for an operator due to repetitive use of the tool.
Another problem that has been common with advancing mechanism for explosive powder actuated tools is complexity requiring a large number of interconnected parts and moving parts to ensure operation of the advancing mechanism.
What is needed is a fastener driving tool which uses the motion of the trigger to drive an automatic indexing of a strip of explosive cartridges, while requiring fewer parts and overcoming the dead stop phenomenon of the prior art.